FIG. 1 is a schematic plane view showing a cell region, a pad region and a connection region of an upper portion of a front surface of a conventional PDP (Plasma Display Panel).
Referring to FIG. 1, a general PDP front panel 10 is briefly classified into a cell region 20 in which a bus electrode (a scan electrode+a sustain electrode) 25 and a back matrix pattern (not shown) are formed, a pad region 30 having a pad block 35 formed around the cell region 20 to electrically connect each bus electrode 25 to an external electrode, and a connection region 40 having a connection wiring 45 for connecting the bus electrode 25 formed in the cell region 20 and the pad block 35 formed in the pad region 30 with each other. Here, the connection wiring 45 is generally inclined diagonally since a gap of the bus electrodes 25 and a gap of the pad blocks 35 are different from each other.
FIG. 2 is a sectional view showing a part of the cell region 20 to illustrate arrangements of bus electrodes X, Y formed in the cell region 20 among three regions shown in FIG. 1.
Referring to FIG. 2, a scan electrode X and a sustain electrode Y make a pair in a strip shape in each cell region 20. Also, electrode pairs (scan electrode X+sustain electrode Y) are successively arranged to configure the entire cell region 20. The scan electrode X and the sustain electrode Y may be formed using photolithography, which however has drawbacks of complicated processes, plenty wasted materials and increased manufacture costs due to the use of a mask. Thus, a method for forming an electrode pattern by ink-jet printing using a multiple nozzle head is recently highlighted. If a scan electrode X and a sustain electrode Y are formed using the ink-jet printing using a multiple nozzle head, it is possible to form several electrode patterns at once.
However, in the conventional electrode pattern forming method using ink-jet printing, the condition for designing gaps of nozzles provided to the multiple nozzle head is not matched with the condition for designing arrangements of scan electrodes and sustain electrodes. Thus, the scan electrode and the sustain electrode cannot be formed at the same time, but a scan electrode forming process and a sustain electrode forming process should be conducted separately. It will be explained below in detail with reference to the figures.
FIG. 3 is a diagram exemplarily showing a design condition for gaps of nozzles provided to a multiple nozzle head and a design condition for arrangements of scan electrodes and sustain electrodes.
Referring to FIGS. 2 and 3, a gap (D1) between scan electrodes (X1 to X3) and a gap (D2) between sustain electrodes (Y1 to Y3) formed in adjacent pixels 20 are generally designed equal to a linear gap (Dp) of the pixels 20, respectively. However, if a gap (Ds) between the scan electrode (X1 to X3) and the sustain electrode (Y1 to Y3) is designed without considering the gap of nozzles provided to a multiple nozzle head as conventionally, it is impossible to jet the scan electrode (X1 to X3) and the sustain electrode (Y1 to Y3) simultaneously. Thus, in the conventional technique, ink jetting for forming the scan electrode (X1 to X3) and the sustain electrode (Y1 to Y3) should be separately conducted after a pitch of nozzles provided to the multiple nozzle head is matched equal to a height (Dp) of the pixel.
The conventional electrode pattern forming method using ink-jet printing shows another problem. Namely, there is much possibility that an electric open circuit occurs in the connection wiring 45 (see FIG. 1) formed in the connection region 40 (see FIG. 1). That is to say, since the gap of bus electrodes formed in the cell region 20 is not equal to the gap of pad blocks formed in the pad region, the connection wiring formed in the connection region is inevitably inclined at a predetermined angle. However, a gap of hit inks is equal to a pitch of nozzles, so the possibility of open circuit is increased in case an inclined line pattern is formed as shown in FIG. 4 rather than the case that a horizontal line pattern is formed. For example, in case the connection wiring is inclined at 45 degrees, an ink hit gap is 1.41 time greater rather than the case that a connection wiring is horizontal, so the possibility of open circuit in the connection wiring is increased by 40%, assuming that the dispersion of ink is identical.
FIG. 5 is a photograph showing a portion of the connection wiring 45 where a open circuit actually occurs. Referring to FIG. 5, it would be found that hit inks are not connected but open-circuited at several points in the connection wiring 45 formed in the connection region 40. If an open circuit occurs in the connection wiring 45, inferior pixels may occur, which is reported as a problem fundamentally unsolved if the design condition for the connection wiring 45 is not improved.